kernfs: drop shared NUMA mempolicy hooks

It seems strange that kernfs should be an outlier with a set_policy and
get_policy in its kernfs_vm_ops.  Ah, it dates back to v2.6.30's commit
095160aee954 ("sysfs: fix some bin_vm_ops errors"), when I had crashed on
powerpc's pci_mmap_legacy_page_range() fallback to shmem_zero_setup().

Well, that was commendably thorough, to give sysfs-bin a set_policy and
get_policy, just to avoid the way it was coded resulting in EINVAL from
mmap when CONFIG_NUMA; but somehow feels a bit over-the-top to me now.

It's easier to say that nobody should expect to manage a shmem object's
shared NUMA mempolicy via some kernfs backdoor to that object: delete that
code (and there's no longer an EINVAL from mmap in the NUMA case).

This then leaves set_policy/get_policy as implemented only by shmem -
though importantly also by SysV SHM, which has to interface with shmem
which implements them, and with SHM_HUGETLB which does not.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Hugh Dickins <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Sidhartha Kumar <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Tejun heo <[email protected]>
Cc: Vishal Moola (Oracle) <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Yosry Ahmed <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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